A system in which a server provides a document in response to a request from a client, such as the world wide web (WWW) that provides a hyper text markup language (HTML) document, has been widely diffused recently. In such a system, reduction in a time required for providing a document to a client, i.e., more specifically, reduction in a time between transmission of a request from a client and display of a document in the client is a problem that has been attempted to be solved for a long time. For example, Patent Literature 1 discloses a technique that caches a content in a web server in order to efficiently use a cache even in the case where access to a memory resource or a web service is limited.